Protein purification methods that involve tagging a protein of interest with an affinity tag are widely used in laboratory settings for R&D applications, but have proven to be impractical for large-scale manufacturing operations. In the bioprocessing industry, only cleavable affinity tags are used to ensure that the final product does not contain the tag, which must be removed during production, typically using a site-specific protease. Removing the affinity tag requires additional process steps, which substantially increases cost and time, particularly at industrial scale. Moreover, inefficient and off-site cleavage leads to contamination of the final protein product with proteins that retain the tag and truncated protein fragments, respectively, which is not acceptable in bioprocessing applications.
Accordingly, there is a need to develop improved affinity chromatography reagents and methods that permit large-scale purification of proteins under industrial conditions.